The benefits of breathing through the nose is that the fine hairs present inside the nose acts as a filter to prevent unwanted particles from entering the lungs. Breathing through the nose also helps to warm and humidify the air which is inhaled. When breathing through the mouth, the benefits of nasal breathing is lost.
Apart from not getting the benefits of nasal breathing, mouth breathing carries a large number of harmful effects. Craniofacial development (the development of the bones of the head and face) is greatly affected with mouth breathing. The tongue has a big role to play in this. During mouth breathing, the tongue adopts a low forward position rather than resting at the palate (roof of the mouth). The picture below shows where the tongue should rest during nasal breathing.
For some children, even as nasal breathers the tongue does not rest at the top of the mouth due to a presence of a tongue tie, poor muscle tone of the tongue or a change in resting posture of the tongue from the extended use of milk bottles and pacifiers during infancy. Breast-fed babies naturally adopt a good resting tongue posture and predominantly nasal breathers.
Due to the low resting posture of the tongue, the upper jaw develops in a forward direction and becomes narrow. More vertical growth is seen in children who mouth breathe leading to long, narrow faces and gummy smiles. The lips which are meant to be together at rest fail to guide the developing teeth in good alignment which also contributes to crowding of teeth.
Apart from poor craniofacial development and crooked teeth, mouth breathing also affects quality of sleep, memory formation and may be contributing factor to learning disorders and neurological disorders. This will be discussed in detail on another post.
Written by Dr Nijamuddeen A. Latiff